This invention relates to a method for isolating 3-hydroxy steroids and 3-keto steroids from mixtures thereof with lipids.
Various methods for isolating steroids from such mixtures are known. For example, in German Pat. No. 827,199, a method for isolation of sterols from mixtures is described wherein the mixture is dissolved, preferably in a hydrocarbon solvent, and is heated with a four- to sixteen-fold excess of anhydrous zinc chloride. After cooling of the solution, the precipitated ZnCl-sterol adduct can be separated out and split into the individual components. British Pat. No. 1,164,769 describes a method for the isolation of sterols from mixtures wherein the mixture is dissolved, preferably in a hydrocarbon solvent, the solution is mixed with an aqueous solution of a metal salt which is suitable for complex formation, the water is progressively removed by azetropic distillation, and the precipitated adduct is isolated and split in a conventional manner after cooling of the mixture.
Such known methods have the disadvantage that they are technically very costly on account of the high reaction temperature (customarily over 100.degree. C.) and that in the isolation of many 3-hydroxy steroids and 3-oxo steroids considerable loss of product is experienced, since these steroids are destroyed under these conditions. In addition, these known methods often have the disadvantage that the recovery of the metal salt used for formation of the adduct, which is necessary in a method carried out on large scale simply with regard to environmental considerations, is often very costly. The technical scale use of hydrocarbon solvents is also not without its drawbacks, since these are rapidly electrostatically discharged, often have a low ignition point and are often very toxic.
Accordingly, there is a need for a method of isolating 3-hydroxy steroids and 3-keto steroids from mixtures containing such compounds without the disadvantage of the known methods.